The present invention relates generally to plastic bags and more particularly to a novel air permeable bag suitable for use in the cultivation of mushroom spawn.
It has been customary in the past to produce mushrooms in plastic bags. This is accomplished by pasturizing a substrate, inoculating the substrate with mushroom spawn seeds, transferring the mixture into plastic bags and after a suitable method of incubation, collecting the mushrooms at maturity. The inoculation is performed by mixing the substrate and the fungus seeds in the open air. This operation also requires for the pasturization room to remain open for several hours. Moreover, since it is highly desirable to prevent contamination of the mushroom from contact with microbes in the air, the transfer of inoculated, pasturized substrate from one container to plastic bags involves some difficulty.
U.S. Pat. No. 2,851,821 discloses mushroom spawn grown in a plastic bag. The bag is closed by turning the ends of the bag and forming a chimney, and it is sealed by placing a wad of cotton or the like in the chimney thus formed. In another embodiment, a tube is inserted in the top of the bag and the bag gathered around the tube of the string. A filter plug is then placed in the tube.
Another method is described in U.S. Pat. No. 4,027,427 wherein the spawn is grown in a plastic bag provided with a temporary filter cover. This bag is provided with a removal closure mechanism for filling the bag and maintaining sterility during the processing steps.
U.S. Pat. No. 4,977,702 discloses a bag for the production of eatable mushrooms which is provided with a number of gas exchange surfaces or membranes which are impervious to outside microorganizms, thereby avoiding contamination of the nutrient substrate by outside microorganisms. Innoculation can be performed by injection of the inoculum in suspension through the plastic bag. The gas exchange membranes of the bag may be made of Dupont Tyvek.RTM. spun bonded polyolefin. U.S. Pat. No. 4,311,477 teaches a bag for cultivating mushrooms constructed, at least in part, from a micro-porous film having gas permeability, but which does not pass bacteria and infectious microbes.
Although it has been found that the above-listed bags are suitable for the production of mushroom spawn, it has also been found that the growth of the spawn is hindered within the bags by the lack of adequate airflow and direction of the airflow at an appropriate volume to the substrate within the bags.
Accordingly, it is an object of the present invention to provide an improved plastic bag for the growth of mushroom spawn which is low in cost, easy to produce and which circulates uncontamininated air to the substrate within the bag in an improved manner, thereby resulting in improved mushroom production rates and quantities.
The following U.S. and foreign references were identified as being relevant to the present invention:
U.S. Pat. Nos. 4,878,312 CHIMICU, 4,977,702 FORTIN ET AL: EP No. 83-742416; JAPAN 2286-012; JAPAN 2-4673; GERMANY 3734-509-A; SWITZERLAND 647-209-A; GREAT BRITAIN 1,176,188 and GERMANY 148-436.